Difficulties may exist in installing fences when there is unequal spacing between fence posts. Unequal spacing between fence posts may happen by ground conditions, shapes of the overall fences, or other reasons. Currently, mounting bracket systems in the market are allows a little or no movement to fix this problem. Besides the difficulty in installing fences, unequal spacing between fence posts is not aesthetically pleasing. There have been attempts to solve the problem using various devices. However, these other devices have not been successful in adjusting uneven field fence installation to completely solve the problems. In addition, these devices may require additional components to install, and therefore require extra labor and create aesthetically not pleasing end-products. The current subject fence post attachment bracket system provides a solution because it is simple and elegant to install. Moreover, embodiments the present disclosure are universally adjustable to round or square metal fence posts, by bolting onto “off the shelf” non-adjustable fence post brackets for various fence materials such as metal fence sections or three rail metal fences.